1. Field of the Disclosure
The present disclosure relates to a liquid crystal display (LCD) device, and particularly, to an LCD device capable of preventing light leakage occurring at peripheral regions of protrusions of a light guide plate during an assembly process.
2. Background of the Disclosure
Among flat panel display devices that have been developed so far, a liquid crystal display (LCD) device is being applied to various fields such as a notebook, a monitor, a television, a spaceship and an airplane.
The LCD device is largely classified into an LC panel, a driving circuit unit, and a backlight unit.
The LC Panel displays an image by controlling the amount of transmissive light. The driving circuit unit applies each kind of signal transmitted from a driving system to the LC panel, and controls the signals. And, the backlight unit serves as a light irradiation device for uniformly irradiating light to the entire part of the LC panel. For enhanced efficiency of the backlight unit in the aspects of a thickness, a weight and power consumption, research is being actively performed.
Since the LCD device is not a spontaneous light emitting display device, an additional optical source such as the backlight unit is required. The backlight unit for the LCD device is categorized into a direct type one and an edge type one.
In the case of the edge type backlight unit, a fluorescent lamp is installed at the periphery of a flat panel, and light is made to be incident onto an entire surface of an LC panel from the fluorescent lamp through a transparent light guide plate. Owing to the light guide plate, the edge type backlight unit has a comparatively thin thickness.
In the case of the direct type backlight unit, an optical source is disposed on a rear surface of an LC Panel to directly irradiate light to the entire surface of the LC panel. Differently from the edge type backlight unit, the direct type backlight unit is provided with a plurality of optical sources, thereby enhancing brightness and implementing a wide light emitting area.
The edge type backlight unit has the following disadvantages.
Firstly, the edge type backlight unit has a weight heavier than the direct type backlight unit due to the light guide plate.
Secondly, the edge type backlight unit has lowered optical efficiency due to light absorbed by the light guide plate to disappear.
On the other hand, the direct type backlight unit has the following disadvantages.
Firstly, the direct type backlight unit requires high power consumption and heat radiation amount due to a plurality of lamps, even if it has higher optical efficiency than the edge type backlight unit.
Secondly, the direct type backlight unit has a thick thickness as the lamps are spacing from optical sheets since there is no light guide plate between the lamps and the optical sheets.
The LCD device requires an optical source such as a backlight unit, optical sheets for enhancing optical efficiency by transmitting light emitted from the optical source to the LC panel, a light guide plate serving as a passage of the light transmitted to the LC panel from the optical source, and a case for supporting and fixing the above components.
The LCD device is fabricated by laminating the optical source, the optical sheets, the light guide plate, etc. onto a rear surface of the LC panel, and then by assembling the LC panel to the case.
The conventional LCD device will be explained with reference to FIGS. 1 and 2.
FIG. 1 is a schematic sectional view of an LCD device in accordance with the conventional art.
FIG. 2 is a planar view schematically showing a state that protrusions formed on both side surfaces of a light guide plate are inserted into locking grooves formed on both side surfaces of a main support, and are fixedly supported by the locking grooves.
Referring to FIG. 1, the conventional LCD device comprises a main support 24, a backlight unit and an LC panel 6 each laminated on the main support 24. The backlight unit includes a light guide plate 16 disposed in the main support 24 for transmitting light emitted from a lamp to the LC panel 6, a reflection sheet 18 disposed on a rear surface of the light guide plate 16, a plurality of optical sheets 14 laminated on the light guide plate 16, and a lamp housing (not shown) disposed to encompass the lamp (not shown).
The LC panel 6 is composed of a color filter substrate 3, an array substrate 5, and an LC layer (not shown) disposed between the color filter substrate 3 and the array substrate 5. An upper polarization sheet 4a is attached to the color filter substrate 3, and a lower polarization sheet 4b is attached to a rear surface of the array substrate 5.
A case top 2 encompasses the edges of the LC panel 6 and the side surfaces of the main support 24 by being coupled thereto.
A guide panel 7 supports the LC panel 6, and fixes the optical sheets 14 by being fixed on an upper surface of the main support 24.
The optical sheets 14 include a lower diffusion sheet 14d for diffusing light emitted from the light guide plate 16 to an entire region, two prism sheets 14b and 14c for making the light diffused by the lower diffusion sheet 14d proceed at an angle perpendicular to the LC panel 6, and an upper diffusion sheet 14a for diffusing the light having passed through the two prism sheets 14b and 14c. 
The reflection sheet 18 reflects light incident thereon through a rear surface of the light guide plate 16, to the light guide plate 16 again, thereby reducing optical loss.
Protrusions 17 are formed on both side surfaces of the light guide plate 16 with a constant gap therebetween. As shown in FIG. 2, as the protrusions are inserted into locking grooves 24a formed on inner side walls of the main support 24, the light guide plate 16 is fixed to the main support 24 to be supported thereby.
An assembly method for the conventional LCD will be explained as follows.
Firstly, the protrusions 17 formed on both side surfaces of the light guide plate 16 are inserted into the main support 24 to be fixed thereto. Then, the optical sheets 14 are assembled onto the main support 24, and the LC panel 6 is mounted on the optical sheets 14. Next, the case top 2 is assembled to encompass the edges of the LC panel 6 and the side surfaces of the main support 24.
However, the conventional LCD device has the following problems.
Firstly, as the LCD device becomes slimmer and smaller, each component has a thin thickness. Due to a thin thickness of the light guide plate, light leakage occurs at the periphery of the protrusions formed on both side surfaces of the light guide plate. Especially, as shown in FIG. 2, a distance (D1) between an image display region (P1) and the protrusions of the light guide plate becomes shorter. In this case, when the light guide plate is not properly assembled to inside of the main support by using the protrusions, light leakage may occur.